This invention relates to a process for producing azoimino ethers which are intermediates for the syntheses of azoguanyl compounds, azoamide compounds, azoester compounds and the like useful as polymerization initiators in the production of polymeric compounds.
Azoguanyl compounds are useful particularly as a polymerization initiator for use in aqueous solutions, because their mineral acid salts are water-soluble. Azoamide compounds are useful as polymerization initiator effectively usable in the non-salt form. Azoester compounds are useful as polymerization initiator excellent in solubility. Azoimino ethers are intermediates of these compounds useful as polymerization initiator. Hitherto, azoimino ethers have been produced by reacting the corresponding azonitrile compound in the presence of hydrogen chloride in an alcoholic solvent, as disclosed in U.S. Pat. No. 2,599,299. This process, however, is disadvantageous from the industrial point of view in that the progress of the reaction often becomes rapid and uncontrollable. On the other hand, as an improvement capable of solving the above-mentioned problem, the process mentioned in Japanese Patent Examined Publication No. 2,230/83 can be referred to. This process comprises reacting an azonitrile with an alcohol in the presence of hydrogen chloride gas in a solvent into which hydrogen chloride gas has a low solubility. According to this process, no rapid reaction takes place and the reaction is quite easy to control. Further, it is economical because it consumes only the approximately theoretical amount of hydrogen chloride. Thus, it can be said to be an industrially quite advantageous production process of azoimino ethers.
At any rate, however, these prior production processes of imino ethers which comprises reacting an azonitrile with an alcohol in the presence of hydrogen chloride gas (including the above-mentioned improvement) use expensive azonitrile and expensive hydrogen chloride gas as the starting materials, and therefore the produced imino ether is naturally expensive and there is a limitation in the cost down of the process. Accordingly, these processes cannot be said to be industrially satisfactory. Thus, it has been desired earnestly to develop a new industrial process capable of giving imino ethers less expensively.